Update Hugo, Docsy, and Node packages

[OlufunkeMoronfolu]

Summary

The following dependency updates were made:

• Hugo Extended from ^0.126.1 to ^0.156.0
• Docsy from 0.10.0 to 0.15.0
• Node.js CI version (.travis.yml): 20.9 to 24.15

CSS fixes (Docsy 0.15 compatibility)

• Overrides Docsy 0.15's new rule that makes all top-level TOC entries bold by default.
• Overrides Docsy 0.15's new hover background colour on TOC links so hover states remain as is.
• Fixes font-weight variable reference: $font-weight-body-text → $td-font-weight-body-text (renamed in Docsy 0.15).

Config fix

• Updated [module] replacements in hugo.toml to reflect the correct module paths for Font Awesome and Bootstrap under the new Hugo/Docsy versions.

Layout fixes (Docsy 0.15 compatibility)

• Added layouts/docs/single.html to route docs single pages to _default/content.html via .Render "content", instead of Docsy's new _td-content.html which renders the page description field as visible body text. This preserves the existing behaviour where description is used for metadata only (search snippets and link previews).

Other fixes

• Duplicate metadata causing build errors
• Fixed feedback partial to now use the full site params context (.Site.Params.ui.feedback) rather than a scoped context (.). In Docsy 0.15, the partial is invoked differently, so {{ .yes }} no longer resolves.